The invention relates to a surgical stapling instrument, which can be used for applying surgical staples or clips to tissue. And particularly the invention relates to an intraluminal surgical stapling instrument for the creation of an anastomosis.
Surgical stapling is known in the art as a quick and efficient way of joining and repairing tissue and has become not only an acceptable but a preferred alternative to suturing.
The known intraluminal surgical stapling instruments typically comprise an elongate shaft having a proximal actuating mechanism and a distal staple fastening assembly mounted to the shaft. The staple fastening assembly typically comprises a staple cartridge device containing a plurality of staples arranged in a circular closed array. A circular cutting knife having a closed cutting edge is contained within the cartridge device and is positioned such that there is at least one closed row of staples on the outside of the cutting edge. The knife can be advanced in an axial distal direction during operation. A trocar shaft extends distally from the cartridge device and is axially movable with respect to the latter. An anvil is detachably mounted to the trocar shaft and comprises a staple forming surface facing the distal end surface of the cartridge device and adapted to form the ends of the staples pushed by a staple driving device against the anvil. The distance between the cartridge end surface and the anvil staple forming face can be varied by an adjustment mechanism mounted to the proximal end of the trocar shaft and configured to move the trocar shaft together with the anvil with respect to the staple cartridge device. The actuating mechanism typically links the staple driving operation to the knife advancing operation such that the tissue contained between the staple cartridge device and the anvil is simultaneously stapled and cut when the actuating mechanism is triggered by the surgeon.
Generally, in the performance of an intraluminal anastomosis, two pieces of lumen or tubular tissue, e.g. intestinal tissue, are joined together by a closed row of staples. In performing the anastomosis with a surgical stapling instrument, the anvil is placed in the proximal end of the distal lumen or tissue portion (from a surgeons viewpoint) and the cartridge device is placed in the distal end of the proximal lumen or tissue portion to be joined. The placement of anvil and cartridge device can be done by inserting them through entry ports cut into the corresponding lumen by the surgeon or by inserting them endoscopically, e.g. transanally through the rectum. The lumens or tissue portions destined to be joint in anastomosis can be tied to the anvil shaft and/or trocar shaft using a suture or other conventional tying technique. Thereafter, the anvil shaft is attached to the trocar shaft of the staple fastening assembly (cartridge device) and the gap between the cartridge device and the anvil is closed, thereby clamping the proximal and distal tissue portions together in the gap. Upon actuation of the intraluminal stapling device one or more closed rows of staples are driven out of corresponding staple guide slots of the cartridge device. The staples are driven through the distal and proximal tissue portions and formed against an array of staple forming grooves of the anvil, thereby joining the tissue portions and forming a tubular pathway.
Simultaneously, as the staples are applied and formed, the circular knife is advanced distally to cut the excess tissue adjacent to the inner annular row of staples. Then, the tissue edge joined by the closed row of staples is unclamped by advancing the trocar shaft distally with respect to the cartridge device to move the anvil away from the cartridge device. The stapling instrument is then withdrawn from the anastomotic site by pulling the anvil proximally through the anastomotic orifice defined by the annularly stapled tissue edges.
Although the use of the known surgical stapling instruments is very beneficial and greatly facilitates the performance of an anastomosis, it involves some problems. Often it is difficult to retract the instrument from the site of the operation, because it is difficult to withdraw the anvil through the anastomotic opening defined by the closed row of staples, which is somewhat stiff. Moreover, after the operation, the incidence of clinical stenosis at the site of the anastomosis is not rare.
In order to overcome these known deficiencies, it is proposed in WO 01/54594 A1 to arrange the closed row of staples in a wavy shape. In this way, the line along which the staples of the closed row are arranged has a greater total length than the projection of this line onto a plane. Consequently, the length of an anastomosis seam is greater than that of an anastomosis performed by means of a conventional stapling instrument. Because of this increased length, the anastomotic site can assume a larger diameter and is more flexible, so that the anvil can be easier moved through the anastomotic opening. Additionally, the resulting larger anastomosis lumen will alleviate the incidence of clinical complications.
Nonetheless the wavy shape of the staple arrangement has some drawbacks. For optimum performance of the stapling instrument, the individual staples are expelled from the cartridge device in a direction perpendicular to the local slope of the wavy shape, which generally is not parallel to the longitudinal axis of the instrument, requiring a complex staple drive device. Moreover, due to the oblique orientation of the staple driving direction with respect to the anvil approximation direction (axial direction of the stapler) the alignment of the staple-forming grooves at the anvil and the staple guide slots of the cartridge device varies undesirably with any variation of the distance between the cartridge device and the anvil, thereby limiting the use of the stapler to only one thickness of tissue to be joined in anastomosis.
Moreover, since the length of the wavy stapled seam can be increased only by increasing the number of waves along the circular staple line and by increasing the amplitude (axial extension) of the waves, the application of wavy circular staplers encounters some limits linked to the physiological peculiarities of the body tissue. By increasing the number of waves (at a given amplitude) along the staple line the gradient of the inclination or flexure of adjacent tissue portions is increased to an extent which might lead to tissue trauma or local rupture. On the other hand, using a staple line having only one single sinusoidal wave, the amplitude of the wave, i.e. the axial distance between the valley and the peak of the single wave, needs to be very high in order to obtain the desired increase of the length of the stapled seam. Since some tubular organs of the human and animal body, particularly the intestine, have an unilateral blood supply, an anastomosis with a great longitudinal extension with respect to the lumen might leave some regions of tissue completely isolated from blood supply, leading to necrosis.
The object of the invention is to provide a surgical stapling instrument for performing an anastomosis, which reconciles the contrasting requirements of maximizing the length of the stapled seam, minimizing the tissue trauma and reducing the complexity of the staple drive device. A further object of the invention is to provide a surgical stapling instrument being adaptable to different tissue thicknesses.